The present invention relates generally to a spring clip for mounting a cooling device to a component to be cooled. More specifically, the present invention relates to a spring clip including swing arms with rocking and force profiles that ensure self-alignment of the cooling device with the component so that a load imparted on the cooling device by the spring clip is applied substantially at a center of the component without restricting freedom of movement of the cooling device.
It is well known in the electronics art to place a heat sink in contact with an electronic device so that waste heat generated by operation of the electronic device is thermally transferred into the heat sink thereby cooling the electronic device. With the advent of high clock speed electronic devices such as microprocessors (xcexcP), digital signal processors (DSP), and application specific integrated circuits (ASIC), the amount of waste heat generated by those devices and the operating temperature of those devices are directly proportional to clock speed. Therefore, higher clock speeds result in increased waste heat generation which in turn increases the operating temperature of the device. However, efficient operation of the device requires that waste heat be effectively removed.
Heat sink devices came into common use as a preferred means for dissipating waste heat from electronic devices such as the types described above. In a typical application, a component to be cooled is carried by a connector that is mounted on a PC board. A heat sink is mounted on the component by attaching the heat sink to the connector using a clip or fasteners, for example. One disadvantage to using fasteners, such as screws or the like, is that holes must be drilled in the PC board to accommodate the screws and the amount of time necessary to mount the heat sink is longer.
Efficient dissipation of heat from the component by the heat sink depends to a large extent on the thermal contact between the heat sink and the component and the contact pressure between the heat sink and the component. Ideally, an attachment device, such as a clip, positions the heat sink so that the a surface of the heat sink that is in contact with the component is substantially flat and the contact pressure between the heat sink and component acts along a load axis that is centered on the component.
However, regardless of the technique used to attach the heat sink to the component, thermal contact and contact pressure can be adversely affected by manufacturing variations in the component, the heat sink, or both. Because the required manufacturing tolerance to obtain a substantially flat mating between the heat sink and the component while centering the load axis on a center of the component fall within a very narrow window and manufacturing variations can adversely impact heat dissipation resulting in inefficient operation of the component or component failure. Furthermore, in general, the attachment device is rigidly connected to the heat sink therefore restricting freedom of movement of the heat sink. The lack of freedom of movement coupled with the manufacturing variations results in a higher thermal resistance between the heat sink and the component.
Consequently, there exists a need for an attachment device that can compensate for manufacturing variations in the component, the heat sink, or both, while allowing for freedom of movement of the heat sink. There is also a need for an attachment device that allows for easy insertion and removal of a heat sink by hand and without the need for tools, fasteners, or the like. Moreover, there is a need for an attachment device that ensures a load axis of the attachment device is coaxial with an axis of the heat sink and with a center of the component to be cooled. Finally, there is a need for an attachment device that is easy to manufacture at a low cost.
The present invention solves the aforementioned problems. The spring clip of the present invention can be made from spring quality material such as steel and can be manufactured using low cost stamping and forming processes. Advantages of the stamping and forming processes include the ability to automate manufacturing of the spring clip so that the spring clip can be produced inexpensively.
Additionally, the stamping and forming processes result in an economy of material usage due to specially designed hinge and latch sides of the spring clip. Moreover, a shape of a handle on the latch side makes it easy to latch and unlatch the spring clip by hand; therefore, eliminating the need to use tools or the like to disassemble the heat sink from the component and/or the spring clip.
The problems associated with centering an axis of the heat sink with the center of the component are solved by load arms with a rocking profile at a load axis of the spring clip that ensure that the heat sink rests flat on the surface of the component and that a load applied by the spring clip is applied substantially at a center of the component and along the load axis.
Swing clearances provided on the load arms provide for manufacturing variations without sacrificing the functional needs of centering the load axis on the center of the component and ensuring flat mounting between the heat sink and the component. Moreover, the spring clip of the present invention can be mounted on round heat sinks as well as flat heat sinks.
In one embodiment of the present invention, the ribs include one or more embossed features that extend outward of the rib and allow for relative movement between the spring clip and the heat sink and increase the strength of the spring clip.
In another embodiment of the present invention, the spring clip can be made from a spring quality material.
In yet another embodiment of the present invention, the ribs have a vertex at a rocking axis of the spring clip and the ribs have a substantially circular profile. The circular profile is defined by a rocking radius of a circle that is substantially tangential with a base plane passing through the rocking axis.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.